Cell type diversification and phenotype convergence underlying white fin-ornamentation of cyprinid fishes

Fate-mapping in zebrafish demonstrated that XL arise directly from xanthophore-like progenitors, a process dependent on gap-junction-mediated communication via Gja5b and Cx39.4. Bulk mRNA sequencing of XL versus progenitor cells revealed upregulation of pteridine biosynthesis genes, notably sepiapterin reductase (spra), whose disruption via CRISPR/Cas9 abrogated white pigment formation in both zebrafish XL and Tanichthys leucophores.

Chemical analyses confirmed enrichment of colorless pteridines, including biopterin and pterin, in tissues containing these cells. Together, our findings demonstrate that convergent white fin patterns in zebrafish and white cloud minnow rely on pteridine-based leucophores, arising via lineage-specific differentiation programs, and underscore the diversity of cellular and molecular strategies underlying white pigmentation in cyprinids.